Week 13 lectures 1-3 skeletal neuro muscular junction

Question 1

how fast can action potentials travel

Answer 1

120 metres/sec

Question 2

how many neurons does the human brain have

Answer 2

100 billion

Question 3

what is needed to open up vesicles

Answer 3

calcium ions , action potential

Question 4

what is the neuromuscular junction

Answer 4

the synapse between a neurone and a skeletal muscle fibre

Question 5

how many steps are involved in the release of a transmitter and what are they and how can they be influenced

Answer 5

there are 5 steps
Synthesis
storage
release
activation
inactivation
They are influenced by drugs and toxins resulting in resulting in either an increase or a decrease of transmission

Question 6

how can drugs enhance synaptic transmission and explain

Answer 6

1) direct stimulation of the post-synaptic receptors by
a) the natural transmitter
b) analogues
2) indirect action via:
a) increased transmitter release
b) inhibition of transmitter removal

Question 7

how can drugs inhibit synaptic transmission and explain

Answer 7

1)blocking synthesis, storage, or release from the presynaptic neuron.
2) Blocking post synaptic receptors

Question 8

what are the names of drugs that directly act on receptors

Answer 8

agonists and antagonists

Question 9

what are agonists and describe them entirely

Answer 9

agonists are drugs, hormones, or transmitters which can bind to specific receptors and initiate a conformational change in the receptor resulting in a biological response.

Question 10

what are the two important properties of agonists and describe them

Answer 10

affinity (the ability of agonists to bind to receptors) and

efficacy (the ability of an agonist, once bound to a receptor, to initiate a biological response.

Question 11

what is an antagonist

Answer 11

antagonists bind to receptors but do not activate them

They posses affinity but not efficacy

they block receptors activation by the agonists

Question 12

what is a competitive antagonist

Answer 12

it competes with the agonist for the “agonists binding site” on the receptor.

Question 13

what is the neurotransmitter at the neuromuscular junction (NMJ)

Answer 13

acetylcholine

Question 14

how are synapses classified

Answer 14

according to the transmitter released from the presynaptic neurone

Question 15

what does it mean if the transmission is cholinergic

Answer 15

the presynaptic neuron synthesises and releases acetylcholine (ACh)

Question 16

What are the 2 classes of cholinoceptors and describe them

Answer 16

1) Nicotinic cholinoceptors (activated by ACh or the tobacco alkaloid nicotine but not the muscarine.

2) Muscarinic cholinoceptors activated by ACh or the fungal alkaloid muscarine but not nicotine

Question 17

how is fast transmission mediated

Answer 17

transmitter-gated ion channels

Question 18

how many subunits are there

Answer 18

5
beta
gamma
delta
2 alpha

Question 19

what flows throw the subunits into the cell

Answer 19

sodium ion cations flow in and potassium out

Question 20

what happens when an agonist binds to the receptor

Answer 20

induces a rapid conformational change to open the channel

Question 21

how quick can signalling happen

Answer 21

milliseconds

Question 22

what does mepps stand for

Answer 22

Miniature end plate potentials

Question 23

what happens when ACh is released from a single vesicle

Answer 23

many nicotinic ACh receptors are activated

Question 24

what happens when the ACh receptors are activated

Answer 24

the associated cation channels open and the Na+ ions flux into the muscle fibre to cause a local depolarisation at the endplate region (ie. a mepp)

Question 25

what does electron microscopy reveal

Answer 25

vesicle in the apparent act of exocytosis

Question 26

what does a black widow spider venom(alpha Latrotoxin, aka -a-LTX) do

Answer 26

it influences spontaneous transmitter release

Question 27

what is exocytosis

Answer 27

vesicle fusion

Question 28

what is endocytosis

Answer 28

recovery of vesicular membrane after fusion

Question 29

what would you expect to see on a mepp recording with a control and with the black widow venom

Answer 29

control: miniature spikes as the transmitter is being released as normal

venom: massive releases in the ACh neurotransmitter causing muscle spasms and massive spikes in the mepp recording

Question 30

what would happen after being bitten by the black widow venom

Answer 30

depletion of vesicles
inhibition of endocytosis
distended terminal
paralysis

Question 31

list the simplified model of fast synaptic transmission

Answer 31

1) Presynaptic action potential
2) A synchronous Ca2+ influx via voltage-gated Ca2+ channels
3) Many vesicles undergo exocytosis releasing a large cloud of acetylcholine
4) Activation of many nicotinic acetylcholine receptors
5) This causes a large depolarization of endplate region of muscle cell (an epp)
6) If the depolarization is large enough it activates postsynaptic voltage-gated sodium channels to initiate an action potential